Using Well Test Analysis Techniques to determine Reservoir ... · Using Well Test Analysis...

Michael Judt, Aberdeen, May 7 2014. Devex 2014 Presentation www.taqaglobal.com

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Michael Judt (TAQA)

DEVEX conference, Aberdeen

7th May 2014

Using Well Test Analysis

Techniques to determine

Reservoir Properties and drained

Volume from the first successful

appraisal well in the Northern Part

of the Pelican Field.

Cormorant Alpha

drilling and production

platform, UK, Northern

North Sea

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Location of the Cormorant Alpha Area licences

Shetland

Islands

The Pelican Main Field

Block 211/26

Main Reservoir: Brent

Production Start up

January 1996

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Pelican Main Top Brent Structure Map

• Sub Sea Field, tied back to Cormorant Alpha Platform

• Formation: Brent, Depth 12000 ft , Water Depth 150 m

• Low Permeability because of Depth

• Production Start up 1996

• OOIP around 500 MMbbl,

• Cumulative Oil to Date: 70.7 MMbbl

• Recovery Factor to Date 14.4%

• Currently 6 producing Wells and 3 Water Injectors

• Liquid Production 10000 bbl/d, Oil 7500 bbl/d

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Main, +- 500 MM OOIP

Shoulder

Head

Egg

Beak / Fish

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The Pelican


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P22S1 CPI Log

• Well found initial Pressure (7485 psia at top Perf’s)

• All Brent sands were perforated.

• Production start up 30 August 2013

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Zone Gross Net NTG Permeability kh Porosity Sw

ft ft mD mDft Frac Frac

Tarbert 16.8 11.5 0.683 35.2 405 0.195 0.191

Upper Ness 112.1 58.0 0.517 251.5 14589 0.149 0.199

Lower Ness 79.9 74.5 0.932 37.7 2808 0.189 0.229

Etive 287.0 85.0 0.296 6.8 580 0.187 0.389

Rannoch 132.8 24.5 0.184 2.3 57 0.159 0.465

Broom 115.2 93.0 0.807 4.0 369 0.147 0.451

Total 743.9 346.5 0.466 54.3 18807 0.169 0.338


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Pelican P22S1 September 2013

Period 1: Flow Test

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Period 1: Flow Test Analysis

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Well Location,

Numerical Model

Distance to Faults:

320 ft, 590 ft

Production Time 304 hrs

Cumulative Production 147 Mbbl

Permability Thickness (Kh) 2060 mDft

Effective Permeability (k) 9.15 mD

Skin -1.93

Radius of Drainage (Rd) 1492 ft

Con. OOIP(based on Rd/4) 6 MMbbl

Con. OOIP(Linear P Decline) 35 MMbbl

Productivity Index 2.3 bbl/psi/d

Time to reach PSS 2-12 Months

This Kh is 10% of the Log Kh


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Period 1: Pressure Build up 13 September

2013

• Short (4 hours) pressure Build up

• Well near two perpendicular Faults

• Distance to faults around 100 ft

• Permeability Thickness 3120 mDft

• Effective Permeability 13.9 mD

• Skin -2.91

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P22S1 November 2013

Period 2: Linear Pressure Decline

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Pressure Decline Rate -0.257 psi/hr



Con. OOIP(Linear P Decline) 90 MMbbl


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P22S1 January 2014

Period 3: Pressure Build Up Survey 19/01/2014

Pressure Build Up No. 9,10

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P22S1 January 2014

Period 3: Pressure Build up No. 09, 10 Analysis

• Asked for 24 hr Pressure Build up

• Got 2x build up 63 / 79 hr long

• Model: Slanted well in a closed Rectangle

• Longest side of rectangle uncertain

• Depletion from P* = 1900 psia

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P22S1 January 2014

Period 3: Pressure Build up No. 09, 10 AnalysisProduction Time 3378 hrs




Skin -1.5



Con. OOIP(Well Test Model) 56 MMbbl

Con. OOIP(P* Mbal) 30 MMbbl


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P22S1 March 2014

Period 4: Further Pressure Build Up Surveys

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P22S1 March 2014

Period 4: Pressure Analysis





Skin -1.48


Connected OOIP(based on Rd/4) 103 MMbbl

Connected OOIP(Well Test Model) 50 MMbbl

Connected OOIP(P* Mbal) 31 MMbbl

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The Pelican North Shoulder is isolated from the Main field, as P22S1 found initial Reservoir pressure.

Well P22S1 has a productivity Index of around 2.0 bbl/psi/d, which is in line with the average well test permeability of 9 – 13 md and is similar to the average productivity of a Pelican Main well.

The Permeability thickness derived from Well Test Analysis is only 10-20% of the Permeability thickness derived from Core / Log Analysis. This is a recurrent Theme in Pelican and the reasons for the large difference are not well understood.

The “dynamically” connected volume to P22S1 is between 31 and 90 MMbbl, the mean volume is around 50 MMbbl.

A variety of techniques to derive the connected volume are available in Reservoir Engineering, but most depend on knowing the drainage area shape and size, which in itself implies knowledge about the connected volume.

Summary and Conclusions

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• TAQA UK Ltd

• Hub 1 Cormorant Alpha Team

Acknowledgements

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